The Retrovirology Services Core was established in 2002 and is co-directed by Drs. John Coffin and Bharat Ramratnam. The Core provides essential services to other CFAR cores in diagnosis and monitoring of HIV infection as well as specimen processing and archiving. The Core provides innovative tools for collaborative studies from its special interests in international HIV resistance monitoring, host factors influencing HIV natural history, using advances in stem cell biology to better understand HIV pathogenesis, and studies of immune activation. The Core will pursue four Specific Aims: (1) To provide essential viral assays and HIV monitoring methods, (2) To develop and support innovative retrovirology services along four thematic areas including a) developing and supporting assays for resistance monitoring and phylogenetics of HIV to characterize the molecular epidemiology of drug resistant HIV-1 transmission; b) identifying host factors that that correlate with HIV-1 burden in vivo using proteomic signatures in collaboration with Prevention Sciences Core; c) advancing our understanding of HIV-1 pathogenesis by modeling disease with induced pluripotent stem (iPS) cells in collaboration with the newly established Center for Stem Cell Biology, and d), quantifying levels of immune activation in collaboration with Nutrition, Metabolism and GI Core; (3) To provide training and mentorship to the local and international CFAR community and build technical capacity at international sites with a focus on non-clade-B transmission and drug resistance, and (4) To support the processing, archiving and distribution of virologic specimens. The Retrovirology core maintains the CFAR specimen repository and has >60,000 samples available for collaborative research with all CFAR sites. Services are prioritized to support CFAR developmental grant awardees and junior investigators.